RESUMO
Objective To explore the effects from different contact areas of the instrument causing trauma on biomechanical response parameters of rabbit skull fractures under quasi-static compression conditions. Methods The rabbits were divided into the scalp preservation group and scalp removal group. Each group was subdivided into 3 mm group, 6 mm group, 9 mm group according to contact diameter of the instrument causing trauma. There were 9 rabbits in each group, 54 rabbits in total. All rabbits were put to death by over anesthesia and made into a skull compression model. An electronic universal material testing machine was used to perform quasi-static compression of rabbit skulls to fractures, and biomechanical response parameters such as ultimate load, deformation under ultimate load and compressive strength of rabbit skulls in each group were detected. Results The differences in ultimate load, deformation under ultimate load, and compressive strength of rabbit skulls in scalp preservation group and scalp removal group under different contact areas were statistically significant. The ultimate load was positively correlated with the contact area, and the compressive strength was negatively correlated with the contact area. No correlation was found between deformation under ultimate load and contact area. For scalp preservation group and scalp removal group, the difference in deformation under ultimate load was statistically significant in the 3 mm contact surface diameter group, and there was no statistical significance in the other groups. Conclusions The contact area is positively correlated with the ultimate load of rabbit skull fracture and negatively correlated with compressive strength, while it has no correlation with deformation under ultimate load and is unrelated to whether the scalp is removed.
RESUMO
Objective To quantitatively explore the influence of knife sharpness on forearm wounds in knife slash cases. Methods The finite element models of the upper limb and knives with 3 degrees of sharpness (with sharp blade, blunt blade, wide blade) were developed based on human CT images and prototype of slash knife. The slash by 3 kinds of knives on the forearm at velocity of 4 m/s and duration of 10 ms was simulated, so as to analyze changes in contact forces, wound dimensions and energy. Results During the slash by knives with sharp, blunt, wide blade, the blades reached the ulna at about 65, 85, 95 ms, respectively. The corresponding slash forces were 846, 1 064 and 1 865 N; the wound lengths were 135.64, 105.47 and 99.23 mm; the wound depths were 38.77, 27.81 and 18.74 mm. With the sharpness of blade decreasing, the wound formation was slowed, the length and depth decreased and the slash force increased. The model system for slash knife with sharp blade had obviously greater total energy and inner energy, but smaller kinetic energy, compared with slash knife with blunt blade and wide blade. Conclusions The method for quantitatively assessing wound formation in knife slash upon the forearm was developed. The research findings deepen the understanding of biomechanical mechanism of wound formation by knife slash, and provide new scientific means for forensic investigation and court trial of knife slash cases.
RESUMO
In the researches of biomechanics for child craniocerebral injury, the research progress of performance parameter detection for brain, skull, cranial suture and dura mater, and the finite element model construction for child's head were reviewed. Meanwhile, the shortcomings of the established finite element model construction of child's head were analyzed. Thus, it is necessary to strengthen the material properties parameter detection of child's head, and establish the relevant database, so as to lay the foundation for establishing an accurate finite element model of child's head.